Updated: 12/14/2021

Hydatid Disease

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  • Snapshot
    • A 55-year-old woman comes to the emergency department complaining of abdominal pain. She states that she has suffered intermittent nausea for 2 years. Then 3 months ago she began to notice right-sided abdominal pain. She denies vomiting, diarrhea, or constipation. She has not been to a doctor in 3 years since she moved from Peru. She has had no surgeries. She takes no medications. On physical examination, there is moderate right upper quadrant tenderness. An ultrasound shows a 5-cm cyst in the right upper lobe of the liver with an irregular, calcified wall.
  • Introduction
    • Clinical definition
      • liver cyst caused by Echinococcus tapeworm
  • Epidemiology
    • Demographics
      • most common form is E. granulosus and E. multilocularis
      • usually acquired during childhood but do not manifest symptoms until adulthood
    • Risk factors
      • geographic
        • South America, Middle East, sub-Saharan Africa, and western China
        • close contacts with dogs and sheep
  • ETIOLOGY
    • Pathogenesis
      • definitive host
        • usually dogs
      • intermediate hosts include
        • sheep, goats, camels, horses, cattle, and swine
      • transmission
        • adult tapeworm inhabits small intestine
        • produces eggs that are expelled in stool
        • eggs ingested by incidental host (fecal-oral transmission)
        • parasites hatch from eggs and penetrate intestinal mucosa to enter blood/lymphatic system
        • migrates to liver or other organs to form hydatid cysts
      • humans are incidental hosts
  • Presentation
    • Symptoms
      • mostly asymptomatic
      • if liver involved
        • 2/3 of the time
        • nausea, vomiting, and right upper quadrant pain
      • if lung involved
        • 25% of the time
        • cough, chest pain, dyspnea, and hemoptysis
    • Physical exam
      • hepatosplenomegaly
  • imaging
    • Ultrasound
      • best initial test
        • inexpensive
        • 90-95% sensitive
      • single anechoic, smooth, and round cyst
      • may have septations
      • may have a thick or irregular wall
      • “eggshell” appearance if calcified
      • may have daughter cysts (peripherally based cyst within a cyst)
    • Computed tomography or magnetic resonance imaging
      • 95-100% sensitivity
      • for greater anatomic detail to establish location and number of cysts, presence of ruptured or calcified cysts, and to guide management
      • better for evaluation of extrahepatic cysts
  • Studies
    • Diagnostic testing
      • studies
        • complete blood count
          • mild eosinophilia
          • mild elevation in liver function labs
        • serologic and antigen assays
          • i.e., enzyme-linked immunosorbent assay (ELISA)
          • can use for primary diagnosis and follow-up after treatment
          • a negative serologic test does not rule out echinococcosis
        • cyst aspiration/biopsy
          • if serologic test indeterminate/negative
          • risk of anaphylaxis and secondary spread of infection
  • Differential
    • Simple cyst
      • distinguishing factors
        • thinner wall, no calcifications, no septations, and no daughter cysts
        • sterile fluid if aspirated
        • negative serology
          • no additional tests necessary if imaging findings are consistent with a simple cyst
    • Cystadenoma or cystadenocarcinoma
      • distinguishing factors
        • rapid growth
        • tumor cells on histopathology
          • biliary-type mucus-secreting cuboidal or columnar epithelium for cystadenoma
          • malignancy changes of inner epithelial lining for cystadenocarcinoma
        • may have elevated levels of carcinoembryonic antigen (CEA)
        • negative serology
  • Treatment
    • First-line
      • albendazole
        • indication
          • single cyst < 5 cm
        • mechanism of action
          • inhibits microtubule assembly
        • adverse effects
          • hepatotoxicity
          • cytopenia
          • alopecia
          • rash
    • Second-line
      • image-guided percutaneous drainage
        • indication
          • cysts 5-10 cm
          • must be done in combination with medical therapy
        • adverse effect
          • risk of seeding
          • risk of anaphylaxis
    • Third-line
      • resection
        • indication
          • cysts > 10 cm
          • complicated cysts
            • associated with rupture, infection, compression/mass effect, biliary fistulae, hemorrhage, multiple daughter cysts, or extrahepatic cysts
        • adverse effect
          • risk of seeding and anaphylaxis less than percutaneous drainage as attempts is to resect the whole cyst
    • Other treatments
      • Mebendazole and praziquantel are less effective
  • Complications
    • Mass effect
      • Budd-Chiari syndrome
      • portal hypertension
      • cholestasis
      • cirrhosis
    • Secondary bacterial infection
    • Cyst rupture
      • presentation
        • fever
        • acute hypersensitivity reaction (i.e., anaphylaxis)
        • obstructive jaundice
        • death

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